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Full text of "Text Book Of Mechanical Engineering"

I2IO

Appendix  VI.

would raise 20 million gallons per 24 hours to a height of 185
feet. Fig. 1063 is plotted from experiments made upon a six-
stage centrifugal pump of 6" aperture, with a wheel 22" diameter.
It will be seen that the efficiency varies with the rate of delivery
in a very remarkable way, the highest values being always
obtained when small quantities are being supplied at high head.

Pp. 7j6 and 738.    Friction of Hydraulic Ram.

Example 79. A hydraulic lift with ram, load, &c., weighs 10 tons-,
the ram is 9" diameter, and the friction in the mechanism is equal to
'05 of the gross load. The accumulator is half a mile away, and is
loaded to 800 Ibs. per sq. in., and the diameter of the supply pipe is
3 ins. Estimate the speed of ascent of the lift, if the loss of head in

the  pipe  is   -    -^    l   feet where ^ is  the water velocity in pipe.
(Board of Education Applied Mechs. Exam., 3rd stage, 1904.)

Let V = speed of lift. Then, comparing areas of rarn and pipe,
9ęz/ = velocity in supply pipe.

Putting loss of head as loss of pressure in 3" supply pipe :

H         -ooo< Lz/j2       -0005 x 5280 x (9z/)2
P = ^ =      2YD"     ^  ............2'3X2X-25         =   184 v* Ibs. per sq. in.

The pressure in rarn will then be 800 - 184 v2 Ibs. per sq. in.

Next equate work inside ram with external work, and we have,

=  10x2240x1*05x2'
/. s/2 = 2*34     and v =   1*53 ft. per m.

(800- 184 -z/2)x~-

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